Open port cylinder on 66cc, why?

burnt yogurt

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I noticed after months of use and problems and really working to get to 25mph...only, I notice that my cylinder has open transfer ports and the high piston hole. There is no windowed piston or reed valves. I have upgraded the plug ngk iridium, cdi and coil, HP aluminum head, and hp dellorto clone carb jetted to .068 for altitude of 3300ft. Plus I drilled the exhaust out some. Still no more than 25 Mph and I only weigh 165lbs. Also its on a 26" mtb. My question is why am I not going faster and why do I have open ports that are stock along with the high hole piston throw. My God it is so annoying!!!!
 
You're welcome here even without an introduction, just because they say that carb is an upgrade doesn't mean that it is, those carbs are known for air leaks. Try your stock carb for a bit.
 
So far today 131 people have traveled to South Africa, where they will shoot lions, pronounce things wrong, visit the Nelson Mandela museum, and attempt to avoid contracting Zika but I am not sure why you have cylinder like that.

Do you have pictures?
 
I noticed after months of use and problems and really working to get to 25mph...only, I notice that my cylinder has open transfer ports and the high piston hole. There is no windowed piston or reed valves. I have upgraded the plug ngk iridium, cdi and coil, HP aluminum head, and hp dellorto clone carb jetted to .068 for altitude of 3300ft. Plus I drilled the exhaust out some. Still no more than 25 Mph and I only weigh 165lbs. Also its on a 26" mtb. My question is why am I not going faster and why do I have open ports that are stock along with the high hole piston throw. My God it is so annoying!!!!
Dellorto clones generally run rich. The #68 would probably work at your elev with a nt, but the dell will probably need a 66.

Most of the open transfer engines I have been seeing have around 3.85 to 4,35 mm of blowdown. You probably also have a bridge in the exhaust port.

If I'm close on these numbers you can use carbide burrs to remove the bridge and raise the exhaust port 1mm. Then use a sanding drum on a dremel tool to ramp the teansfer port positions of the piston 1mm down from the top. This will keep the blowdown the same and increase the exhaust and transfer duration and flow.
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I noticed after months of use and problems and really working to get to 25mph...only, I notice that my cylinder has open transfer ports and the high piston hole. There is no windowed piston or reed valves. I have upgraded the plug ngk iridium, cdi and coil, HP aluminum head, and hp dellorto clone carb jetted to .068 for altitude of 3300ft. Plus I drilled the exhaust out some. Still no more than 25 Mph and I only weigh 165lbs. Also its on a 26" mtb. My question is why am I not going faster and why do I have open ports that are stock along with the high hole piston throw. My God it is so annoying!!!!
Many questions to have answered here.

I tend to specialise mostly with stock to semi-stock builds...I can only build "on the cheap" since i live on just Social Security at my age and cant afford the "big" money builds that others out here can afford to do...I leave the specialised, more sophisticated builds to the real professionals out here.

First is what engine did you buy?...Where did you get it from?...How many teeth/tooth is the rear sprocket?...How many miles do you have on it already, IE is it broken in yet?, What is the gas/oil ratio you are running?...What bike frame type did you build it on?...What notch is your needle valve on your carbie set on?...I see you have made modifications from stock before break-in was begun, just a guess here on my part.

I built mine using a stock, 26 inch Hyper Bike Company bicycle bought from Walmart,

I bought and installed a Zeda 80 motor from bicycle-engines.com with a stock NT carbie with what i assume is a stock .070 jetting...Needle valve is set at the top notch for leanest setting because of my altitude, and my NGK-B6HS plug is gapped at 25 thousandths and burning a perfect chocolate brown...(Pic attached)...And stock exhaust with no modifications, and a 36 tooth rear sprocket with a spring actuated rear tensioner.

I broke it in with CONVENTIONAL 2 cycle Valvoline oil at a 20:1, (6 ounces per gallon) mix along with Amsoil Dominator Octane Boost additive at one ounce per gallon and did this for the first three tankfulls of gas, (Not three gallons, but three tankfulls).

Thereafter break-in, Im at 32:1, (4 ounces of Amsoil Dominator 2 cycle racing oil per gallon), plus one ounce of Amsoil Dominator Octane Boost per gallon of gas.

I live at 4500 ft in Alamogordo, NM in the high desert and regularly ride as high as 9000 ft.

I can ride going uphill at 32 MPH...On a flat i have run at 47 MPH before chickening out, with throttle left over, that i know i can go at least 50 MPH.

Give some more information starting at the very beginning so as to be more helpful to you, as well as why did you make the modifications that you have done already...Im supplying pics below for you to see what i built so you know what im doing this with...The bike weighs 80 pounds and I weigh 215 pounds and im 65 years old...I remember when dirt was clean im so old...lol...DAMIEN
 

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